Copper and stainless steel welding technology operation

The welding of copper and stainless steel is often encountered, and the welding is difficult. The main performance is that it is very sensitive to the penetration crack of copper during welding. ; The second is to choose the appropriate filling material, control the elements that are prone to low-melting eutectic, such as: S, P, O, etc., and add Al, Si, Mn, V, Mo, Ni and other elements to the weld.

manual arc welding

When manual arc welding is used for copper and stainless steel, be aware that if you choose austenitic stainless steel electrodes, it is easy to cause hot cracks; it is best to choose nickel-copper electrodes (70% nickel + 30% copper), or nickel-based alloy electrodes, and copper electrodes ( T237); When welding, the welding process of small diameter and small current is used for fast welding without swinging, and the arc is biased to the copper side to avoid penetration cracks

submerged arc welding

When submerged arc welding is used for copper and stainless steel, the main problems are cracks and pores; the surface of the weldment and welding wire must be strictly cleaned before welding. For weldments with a thickness of 8 to 10mm, a 70°V-shaped groove is generally opened. The breaking angle is 40°, the groove angle on the side of the stainless steel (1Cr18Ni9Ti) is 30°, the flux is HJ431 or HJ430 (baking at 200°C for 2 hours), the welding wire is generally copper wire, and 1 to 3 nickel wires or Nickel-copper alloy wire; choose a larger welding line energy, and use a cooling water type copper pad, the welding wire points to the copper side, and is 5-6mm away from the center of the groove

Tungsten arc welding (TIG)

When copper and its alloys are welded with stainless steel by argon tungsten arc welding, good welded joints can be obtained, but satisfactory results can only be obtained by mastering the appropriate process; the basic form of their welded joints has two types of butt joints and fillet joints. There is no bevel on the copper side, and half a V bevel is best on the stainless steel side.

Clean the surface of the weldment before welding, apply flux (70%H3BO3, 21%Na2B4O2, 9%CaF2) on the front and back, and weld after drying. The welding wire should be Monel alloy (70%Ni, 30%Cu), or Copper alloy welding wire containing silicon and aluminum, such as: HS221, QAl9-2, QAl9-4, QSi3-1, QSn4-3, etc.; when TIG welding, the tungsten arc is biased towards the copper side and the distance from the center of the groove is about 5-8mm. Control the melting amount of stainless steel; most of the welding materials are copper welding wire or copper-nickel welding wire, and bronze welding wire containing aluminum can also be selected, which is to improve the mechanical properties of the weld metal and prevent copper penetration cracks; usually use fast welding, not Swing method; when using the argon arc welding-brazing process, minimize the amount of melting on the stainless steel side, which is equivalent to a brazing connection for the stainless steel, and a fusion welding connection for the copper side.

Gas welding

When copper and stainless steel are welded by gas, since the temperature of the gas welding flame is not as high as that of the arc, it may cause uneven melting of the base metals on both sides due to different melting points, widening of the heat-affected zone, increased deformation, and even lack of fusion; When pure copper and 18-8 stainless steel are used, HSCuZn-2, HSCuZn3, HSCuZnNi and other welding wires are usually used, and 301 welding powder (brazing powder) or borax is used for welding with a neutral flame; A layer of brass is first surfacing on the groove surface on one side, and then welded.

Brazing

When copper and stainless steel are brazed, the solder used is mainly silver-based solder, such as HL302, HL309, HL312, etc. The process method is similar to that of general brazing. It should be noted that the temperature on the stainless steel side should not be too high. Towards the copper side.